The Audio-Technica 4-Channel 48V Phantom Power Supply CP-8506 is exactly what the name states.  The unit is to be used when you need some sort of external phantom power for your console, mixer, or other device.  I briefly owned the CP-8506 a number of years ago in tandem with a portable mixer that I wanted to use more condenser microphones with and didn't have enough phantom power.  However, now there are very few scenarios where I could see something like this being necessary, as most devices will have enough phantom power already built in where something like this would not be necessary.  I'm not even sure if they still make the CP-8506.  The price I paid wasn't as cheap as I would have liked it to be, but the unit definitely did get the job done for what I wanted it for.  It has simple XLR connections for each of the four channels, so you can easily route through to this from your system.  The CP-8506 is built very well and is a piece of equipment that I can't imagine breaking unless you were to drop it or something like that.  Again, it is hard for me to recommend something like this as it is simply something that should be gotten out of necessity and for no other reason.  It isn't like this will provide you with 'better' phantom power or something like that, it does its job well and nothing else.  Since I can't compare it to any other unit in terms of price, I would have to say that this is probably a good deal as it won't cost all that much money.  I don't know of too many other models in terms of external phantom power supplies, but if you need some more phantom power outside of your system for whatever reason, the Audio-Technica 4-Channel 48V Phantom Power Supply CP-8506 will do the job well without issues.